The VUM axons project abnormally in mutant embryos. Variable defects in the projection pattern can be seen in every neuromere. In approximately 20% of embryos, the VUM axons project normally to the posterior commissure but do not follow the correct path once they have reached the anterior commissure. In approximately 30% of embryos, severe VUM projection defects are seen from early stages onward. In the remaining embryos, the projection defects are such that the VUM axons cannot be discriminated from other neuronal processes. The number of midline neurons is normal in mutant embryos, but their position is slightly altered. Longitudinal connectives do not form properly in mutant embryos and axons are occasionally seen to cross the midline. Defects can be seen during early stages of axonal outgrowth. No gross alterations are seen in the number or fate of cortical neurons. The longitudinal glial cells are present in their normal number but are displaced and concentrated at the commissures. A slight reduction in the number of all sensory neurons and changes in their cellular morphology is seen in the peripheral nervous system of mutant embryos. The size of the segmental nerves is reduced, however the axonal projections toward the ventral nerve cord appear normal. A severe reduction in the number of muscle fibres is seen in mutant embryos. In addition midgut formation is affected. The organisation of the F-actin cytoskeleton is abnormal in mutant embryos. The regular appearance of the cytoskeleton is disrupted in both mesoderm and ectoderm.

Mutant embryos show a clear fusion of commissures and frequent disruption of longitudinal connectives. Midline glial cells are either reduce in number or fail to properly migrate in between anterior and posterior commissures. General embryonic morphology is relatively normal, though the PNS shows a slight reduction in sensory neurons and defects in the trajectories of motoneurons.